/*
    datepickr - pick your date not your nose
    Copyright (c) 2010
 */

function datepickr(id, userConfig) {
	var config = {
		fullCurrentMonth : true,
		dateFormat : 'F jS, Y'
	}, currentDate = new Date(),
	// shortcuts to get date info
	get = {
		current : {
			year : function() {
				return currentDate.getFullYear();
			},
			month : {
				integer : function() {
					return currentDate.getMonth();
				},
				string : function(full) {
					var date = currentDate.getMonth();
					return monthToStr(date, full);
				}
			},
			day : function() {
				return currentDate.getDate();
			}
		},
		month : {
			integer : function() {
				return currentMonthView;
			},
			string : function(full) {
				var date = currentMonthView;
				return monthToStr(date, full);
			},
			numDays : function() {
				// checks to see if february is a leap year otherwise return the
				// respective # of days
				return (get.month.integer() == 1 && !(currentYearView & 3) && (currentYearView % 1e2 || !(currentYearView % 4e2))) ? 29
						: daysInMonth[get.month.integer()];
			}
		}
	},
	// variables used throughout the class
	weekdays = [ 'Sun', 'Mon', 'Tues', 'Wednes', 'Thurs', 'Fri', 'Satur' ], months = [
			'January', 'February', 'March', 'April', 'May', 'June', 'July',
			'August', 'September', 'October', 'November', 'December' ], daysInMonth = [
			31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ], suffix = {
		1 : 'st',
		2 : 'nd',
		3 : 'rd',
		21 : 'st',
		22 : 'nd',
		23 : 'rd',
		31 : 'st'
	}, element, container, body, month, prevMonth, nextMonth, currentYearView = get.current
			.year(), currentMonthView = get.current.month.integer(), i, x, buildCache = [];

	function build(nodeName, attributes, content) {
		var element;

		if (!(nodeName in buildCache)) {
			buildCache[nodeName] = document.createElement(nodeName);
		}

		element = buildCache[nodeName].cloneNode(false);

		if (attributes != null) {
			for ( var attribute in attributes) {
				element[attribute] = attributes[attribute];
			}
		}

		if (content != null) {
			if (typeof (content) == 'object') {
				element.appendChild(content);
			} else {
				element.innerHTML = content;
			}
		}

		return element;
	}

	function monthToStr(date, full) {
		return ((full == true) ? months[date]
				: ((months[date].length > 3) ? months[date].substring(0, 3)
						: months[date]));
	}

	function formatDate(milliseconds) {
		var formattedDate = '', dateObj = new Date(milliseconds), format = {
			d : function() {
				var day = format.j();
				return (day < 10) ? '0' + day : day;
			},
			D : function() {
				return weekdays[format.w()].substring(0, 3);
			},
			j : function() {
				return dateObj.getDate();
			},
			l : function() {
				return weekdays[format.w()] + 'day';
			},
			S : function() {
				return suffix[format.j()] || 'th';
			},
			w : function() {
				return dateObj.getDay();
			},
			F : function() {
				return monthToStr(format.n(), true);
			},
			m : function() {
				var month = format.n() + 1;
				return (month < 10) ? '0' + month : month;
			},
			M : function() {
				return monthToStr(format.n(), false);
			},
			n : function() {
				return dateObj.getMonth();
			},
			Y : function() {
				return dateObj.getFullYear();
			},
			y : function() {
				return format.Y().substring(2, 4);
			}
		}, formatPieces = config.dateFormat.split('');

		for (i = 0, x = formatPieces.length; i < x; i++) {
			formattedDate += format[formatPieces[i]] ? format[formatPieces[i]]
					() : formatPieces[i];
		}

		return formattedDate;
	}

	function handleMonthClick() {
		// if we go too far into the past
		if (currentMonthView < 0) {
			currentYearView--;

			// start our month count at 11 (11 = december)
			currentMonthView = 11;
		}

		// if we go too far into the future
		if (currentMonthView > 11) {
			currentYearView++;

			// restart our month count (0 = january)
			currentMonthView = 0;
		}

		month.innerHTML = get.month.string(config.fullCurrentMonth) + ' '
				+ currentYearView;

		// rebuild the calendar
		while (body.hasChildNodes()) {
			body.removeChild(body.lastChild);
		}
		body.appendChild(buildCalendar());
		bindDayLinks();

		return false;
	}

	function bindMonthLinks() {
		prevMonth.onclick = function() {
			currentMonthView--;
			return handleMonthClick();
		}

		nextMonth.onclick = function() {
			currentMonthView++;
			return handleMonthClick();
		}
	}

	// our link binding function
	function bindDayLinks() {
		var days = body.getElementsByTagName('a');

		for (i = 0, x = days.length; i < x; i++) {
			days[i].onclick = function() {
				element.value = formatDate(new Date(currentYearView,
						currentMonthView, this.innerHTML).getTime());
				close();
				return false;
			}
		}
	}

	function buildWeekdays() {
		var html = document.createDocumentFragment();
		// write out the names of each week day
		for (i = 0, x = weekdays.length; i < x; i++) {
			html.appendChild(build('th', {}, weekdays[i].substring(0, 2)));
		}
		return html;
	}

	function buildCalendar() {
		// get the first day of the month we are currently viewing
		var firstOfMonth = new Date(currentYearView, currentMonthView, 1)
				.getDay(),
		// get the total number of days in the month we are currently viewing
		numDays = get.month.numDays(),
		// declare our day counter
		dayCount = 0, html = document.createDocumentFragment(), row = build('tr');

		// print out previous month's "days"
		for (i = 1; i <= firstOfMonth; i++) {
			row.appendChild(build('td', {}, '&nbsp;'));
			dayCount++;
		}

		for (i = 1; i <= numDays; i++) {
			// if we have reached the end of a week, wrap to the next line
			if (dayCount == 7) {
				html.appendChild(row);
				row = build('tr');
				dayCount = 0;
			}

			// output the text that goes inside each td
			// if the day is the current day, add a class of "today"
			row
					.appendChild(build(
							'td',
							{
								className : (i == get.current.day()
										&& currentMonthView == get.current.month
												.integer() && currentYearView == get.current
										.year()) ? 'today' : ''
							}, build('a', {
								href : 'javascript:void(0)'
							}, i)));
			dayCount++;
		}

		// if we haven't finished at the end of the week, start writing out the
		// "days" for the next month
		for (i = 1; i <= (7 - dayCount); i++) {
			row.appendChild(build('td', {}, '&nbsp;'));
		}

		html.appendChild(row);

		return html;
	}

	function open() {
		document.onclick = function(e) {
			e = e || window.event;
			var target = e.target || e.srcElement;

			var parentNode = target.parentNode;
			if (target != element && parentNode != container) {
				while (parentNode != container) {
					parentNode = parentNode.parentNode;
					if (parentNode == null) {
						close();
						break;
					}
				}
			}
		}

		bindDayLinks();
		container.style.display = 'block';
	}

	function close() {
		document.onclick = null;
		container.style.display = 'none';
	}

	function initialise(userConfig) {
		if (userConfig) {
			for ( var key in userConfig) {
				if (config.hasOwnProperty(key)) {
					config[key] = userConfig[key];
				}
			}
		}

		var inputLeft = inputTop = 0, obj = element;
		if (obj.offsetParent) {
			do {
				inputLeft += obj.offsetLeft;
				inputTop += obj.offsetTop;
			} while (obj = obj.offsetParent);
		}

		container = build('div', {
			className : 'calendar'
		});
		container.style.cssText = 'display: none; position: absolute; top: '
				+ (inputTop + element.offsetHeight) + 'px; left: ' + inputLeft
				+ 'px; z-index: 9999;';

		var months = build('div', {
			className : 'months'
		});
		prevMonth = build('span', {
			className : 'prev-month'
		}, build('a', {
			href : '#'
		}, '&lt;'));
		nextMonth = build('span', {
			className : 'next-month'
		}, build('a', {
			href : '#'
		}, '&gt;'));
		month = build('span', {
			className : 'current-month'
		}, get.month.string(config.fullCurrentMonth) + ' ' + currentYearView);

		months.appendChild(prevMonth);
		months.appendChild(nextMonth);
		months.appendChild(month);

		var calendar = build('table', {}, build('thead', {}, build('tr', {
			className : 'weekdays'
		}, buildWeekdays())));
		body = build('tbody', {}, buildCalendar());

		calendar.appendChild(body);

		container.appendChild(months);
		container.appendChild(calendar);

		document.body.appendChild(container);
		bindMonthLinks();

		element.onfocus = open;
	}

	return (function() {
		element = document.getElementById(id);
		initialise(userConfig);
	})();
}